(a) Field of the Invention
The present invention relates to a differential Colpitts voltage controlled oscillator for improving negative resistance, and more particularly, to a voltage controlled oscillator for improving negative resistance of a Colpitts oscillator.
(b) Description of the Related Art
In recent years, a complementary metal-oxide semiconductor (CMOS) process technology has been rapidly being developed according to a request for integration by technological convergence. However, low voltage and an increase of flicker noise by the CMOS process technology are being magnified as a problem to be solved in order to design an analog circuit. In particular, a decrease of output voltage and the increase of the flicker noise may cause deterioration of phase noise performance at the time of designing a voltage controlled oscillator by the CMOS process technology.
As such, a Colpitts voltage controlled oscillator is being attracting attention as a structure for solving the problem caused at the time of designing the voltage controlled oscillator by the CMOS process technology, but start-up current and power consumptions may be large and the phase noise performance may deteriorate due to small oscillation amplitude.
Accordingly, a design technology of a voltage controlled oscillator is required, which is capable of reducing the start-up current and power consumptions and improving the phase noise performance of the oscillator at the operating point of the maximum saturation region.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.